This is a Mayfair window beading regularly used in the late 1980's early 1990's throughout the Southwest. It has gotten brittle and dry and falls apart once removed.
Paul from SWISCO responded:
April 17, 2018
Thanks for posting! I was able to narrow it down to two possible types of glazing. See our 55-006 and 55-030. You will need to compare your dimensions to ours to confirm the better match. Let me know what you think.